1. Field of the Invention
The present invention relates to an ink liquid supply system for an ink jet system printer.
2. Description of the Prior Art
Generally, in an ink jet system printer and, more specifically, in an ink jet system printer of the charge amplitude controlling type, ink liquid is sent from an ink liquid reservoir to a nozzle under a predetermined pressure when a print operation is performed. When the ink jet system printer ceases its operation, the ink liquid supply from the ink liquid reservoir to the nozzle is terminated.
In a system wherein the issuance of the ink liquid from the nozzle is gradually reduced when the ink jet system printer ceases its operation, there is a possibility that the ink liquid will drip from the tip end of the nozzle. This will cause the system to operate erroneously or break down, since the insulation of the system can not be maintained.
Accordingly, it is required that the issuance of the ink liquid from the nozzle will be suddenly terminated when the ink jet system printer ceases its operation. A typical system to perform sudden termination of the ink issuance from the nozzle is disclosed in U.S. Pat. Np. 4,007,684 "INK LIQUID WARMER FOR INK JET SYSTEM PRINTER" issued on Feb. 15, 1977, wherein an electromagnetic cross valve is provided for controlling the supply direction of the ink liquid. When the ink jet system printer ceases its operation, negative pressure is created at the nozzle by the electromagnetic cross valve to return the ink liquid from the nozzle.
In the above-mentioned type of ink liquid supply system, the ink liquid surface comes into contact with the air at the interior of the nozzle when the ink jet system printer is not performing a print operation. Therefore, there is a possibility that the ink liquid will solidify within the nozzle. This will block the orifice of the nozzle when the ink jet system printer begins to operate after interruption of print operation for a considerably long period of time.